This application is related to U.S. patent application Ser. No. 578,787 filed Feb. 10, 1984 and entitled "DIGITAL-TO-ANALOG CONVERTER DEVICE" by Masaharu Kobayashi and five others and assigned to the assignee of this application.
This invention relates to signal conversion apparatus for use in a PCM signal processing system and more particularly to a PCM signal conversion apparatus particularly useful for conversion between simultaneous sampling PCM signal data and alternate sampling PCM signal data.
In the conventional PCM signal format for a two channel system, an L-channel analog signal and an R-channel analog signal may be sampled at simultaneous time points (simultaneous sampling) or otherwise may be alternate time points (alternate sampling). And, most of the PCM signal processing systems are of the type receiving alternate sampling PCM signals for simplification of their circuit construction.
Therefore, for a connection or coupling between processing systems adapted for reception of simultaneous sampling PCM signals and for reception of alternate sampling PCM signals, it will be necessary to "convert" sampling time points for the PCM digital signals, thereby matching the sampling points for PCM digital signals communicated between the processing systems.
Further, a similar problem will arise in connection with a PCM broadcasting from a broadcast satellite using the SHF band and the reception of the broadcast by a receiver on the ground. This satellite broadcasting system is being put into practice in Japan. Namely, the broadcasting from the satellite is to be performed in two PCM transmission modes: the four channel transmission with a sampling frequency of 32 KHz, and the two channel transmission with a sampling frequency of 20 KHz. And in either one of transmission modes, the sampling time points for the PCM transmission signals may not be always concurrent with those for the PCM signals which receivers on the ground will accept.